如何使用Xcode11.2在SwiftUI中创建UItoolbar

import SwiftUI

struct ContentView: View {
    @State private var showToolbar = false
    
    var body: some View {
        NavigationView {
            Text("Hello, SwiftUI!")
                .navigationBarTitle("My App")
                .toolbar {
                    ToolbarItem(placement: .bottomBar) {
                        Button(action: {
                            // 添加按钮的点击事件
                        }) {
                            Image(systemName: "square.and.arrow.up")
                        }
                    }
                    
                    ToolbarItem(placement: .bottomBar) {
                        Spacer()
                    }
                    
                    ToolbarItem(placement: .bottomBar) {
                        Button(action: {
                            // 添加按钮的点击事件
                        }) {
                            Image(systemName: "square.and.arrow.down")
                        }
                    }
                }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}